[PATCH v2 08/13] sh: rework sync_file_range ABI

Arnd Bergmann
2024-06-24T16:38:12Z

The unusual function calling conventions on SuperH ended up causing
sync_file_range to have the wrong argument order, with the 'flags'
argument getting sorted before 'nbytes' by the compiler.

In userspace, I found that musl, glibc, uclibc and strace all expect the
normal calling conventions with 'nbytes' last, so changing the kernel
to match them should make all of those work.

In order to be able to also fix libc implementations to work with existing
kernels, they need to be able to tell which ABI is used. An easy way
to do this is to add yet another system call using the sync_file_range2
ABI that works the same on all architectures.

Old user binaries can now work on new kernels, and new binaries can
try the new sync_file_range2() to work with new kernels or fall back
to the old sync_file_range() version if that doesn't exist.

Cc: stable@vger.kernel.org
Fixes: 75c92acdd5b1 ("sh: Wire up new syscalls.")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/sh/kernel/sys_sh32.c | 11 +++++++++++
arch/sh/kernel/syscalls/syscall.tbl | 3 ++-
2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/sh/kernel/sys_sh32.c b/arch/sh/kernel/sys_sh32.c
index 9dca568509a5..d6f4afcb0e87 100644
--- a/arch/sh/kernel/sys_sh32.c
+++ b/arch/sh/kernel/sys_sh32.c
@@ -59,3 +59,14 @@ asmlinkage int sys_fadvise64_64_wrapper(int fd, u32 offset0, u32 offset1,
(u64)len0 << 32 | len1, advice);
#endif
}
+
+/*
+ * swap the arguments the way that libc wants them instead of
+ * moving flags ahead of the 64-bit nbytes argument
+ */
+SYSCALL_DEFINE6(sh_sync_file_range6, int, fd, SC_ARG64(offset),
+ SC_ARG64(nbytes), unsigned int, flags)
+{
+ return ksys_sync_file_range(fd, SC_VAL64(loff_t, offset),
+ SC_VAL64(loff_t, nbytes), flags);
+}
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index bbf83a2db986..c55fd7696d40 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -321,7 +321,7 @@
311 common set_robust_list sys_set_robust_list
312 common get_robust_list sys_get_robust_list
313 common splice sys_splice
-314 common sync_file_range sys_sync_file_range
+314 common sync_file_range sys_sh_sync_file_range6
315 common tee sys_tee
316 common vmsplice sys_vmsplice
317 common move_pages sys_move_pages
@@ -395,6 +395,7 @@
385 common pkey_alloc sys_pkey_alloc
386 common pkey_free sys_pkey_free
387 common rseq sys_rseq
+388 common sync_file_range2 sys_sync_file_range2
# room for arch specific syscalls
393 common semget sys_semget
394 common semctl sys_semctl
--
2.39.2